"This mission had created a difficult decision for Rincewind, when he'd been presented with the task of preventing Charles Darwin being stung to death by wasps. Right from the start it was obvious that Darwin would see him, and if Rincewind was invisible the wasps wouldn't see him. He'd therefore undertaken the mission carrying two buckets of warm jam and wearing a pink tutu, an acid-green wig, and a red nose, reasoning that (a) Darwin wouldn't believe that he had seen him and in any case (b) wouldn't dare tell anyone..."